Genetics Home > Klinefelter Syndrome
While many men have an extra X chromosome, not a lot actually have symptoms of Klinefelter syndrome. Many men live out their lives without ever suspecting that they have an additional chromosome.
When an extra chromosome does cause Klinefelter syndrome symptoms, the symptoms can vary among individual males. Some men may have many symptoms; others only a few.
Symptoms of this condition can include:
- Breast development (gynecomastia). Ten percent of males with Klinefelter syndrome will develop breasts large enough to embarrass them.
- Reduced facial and body hair.
- Infertility (see Klinefelter Syndrome and Infertility).
- Small testes.
- Being taller than their father or brothers.
- Learning disabilities.
- Problems with speech and language development.
(Click Klinefelter Syndrome Symptoms for more information.)
Because they often don't appear any different from anyone else, many males with the XXY chromosome arrangement probably never learn of their extra chromosome. However, if a Klinefelter diagnosis is to be made, chances are greatest that it will be made at one of the following times in life:
- Before or shortly after birth
- Early childhood
For males in which Klinefelter syndrome is suspected, a special blood test is recommended to confirm the diagnosis.
(Click Diagnosing Klinefelter Syndrome for more information.)